The present disclosure relates to a drum supporting structure for supporting photosensitive drums, image forming apparatuses having the drum supporting structure, and bearings for supporting the photosensitive drums.
To date, in image forming apparatuses such as printers and copy machines, a drum unit including a photosensitive drum has been detachably mounted. Further, in some image forming apparatuses, the photosensitive drums are inserted from above image forming apparatus bodies. In this type of image forming apparatus, the drum unit may be fixed (positioned) by using the following structure.
The apparatus body includes a pair of side plates by which the drum unit is supported. Each of the paired side plates has a cut portion extending in the up-down direction. Further, the apparatus body includes a driving motor, and an apparatus-body-side gear which is driven to rotate by the driving motor. On the other hand, a large-diameter gear that reduces a rotation rate of the driving motor to a predetermined rotation rate for the photosensitive drum is mounted to a rotation shaft of the photosensitive drum. This is for assuredly matching the rotation rate of the photosensitive drum with the rotation rate of the large-diameter gear, to prevent an error therebetween. The rotation shaft of the photosensitive drum is fitted into the cut portions formed on the pair of side plates, thereby mounting the drum unit to the apparatus body. At this time, the apparatus-body-side side gear and the large-diameter gear mesh with each other, and a rotation rate of the driving motor is reduced at a predetermined reduction ratio by the large-diameter gear, thereby transmitting the rotational power of the driving motor to the photosensitive drum.